1. Field of the Invention
The present invention relates to a frame of a cell of a redox flow battery, the frame including an opening that is bordered by a rim, wherein at said rim, a first flow blocker is arranged at the rim which extends into the opening, and further including a distribution channel ending in the opening for supplying or discharging electrolyte liquid to or from the cell, and a semi-cell and a redox flow battery includinq such a frame.
2. The Prior Art
A known embodiment of a redox flow battery 50 or a stack 32 of a redox flow battery 50 is illustrated in the FIGS. 3 and 4. The cells 30 of such a stack 32 usually consist of two adjacent half cells 30a, 30b, wherein each half cell 30a, 30b is formed in each case from a frame 1 which has an opening 8 in which in each case one electrode 20 is arranged and wherein the half cells 30a, 30b are separated at least in the region of the opening 8 by a semi-permeable diaphragm 24. A first electrolyte liquid flows through the first half cell 30a of a cell 30 and a second electrolyte liquid flows through the second half cell 30b of said cell, wherein through electrochemical processes, electric current is generated which can be tapped via electrical connections 48 at the end plates 46 of the stack 32. In some types of redox flow batteries 50 such as, e.g. a vanadium redox battery or a vanadium/polyhalide battery, the two electrolyte liquids are chemically largely similar or have just a different oxidation state (e.g., V2+and V3+, VO2+and VO2+). This process can also be reversed, whereby the electrolyte liquid (or the battery) is charged. A plurality of such cells 30 are combined in a redox flow battery 50 to form a stack 32 by arranging the individual cells 30 next to each other so as to achieve a higher power or voltage. The individual cells 30 are separated from each other by bipolar plates 22. The two electrolyte liquids with different charge states are supplied or discharged via connections 47 in the end plates 46 and conveyed through bores 2, 3 into the frame 1 and through the cells 30. The cells 30 are arranged between the two endplates 46 or the pressure plates 45 resting thereon and can be pressed against each other by bolts 40 extending therethrough, which bolts are tightened by nuts 42, washers 43 and springs 41. Also, a plurality of stacks 32 can be combined in one redox battery 50, wherein a group of stacks 32 electrically connected in series is also called strings and a plurality of strings can be operated electrically in parallel. Such arrangements are well known in many different embodiments.
For increasing the efficiency or the energy efficiency of a redox battery, it is of course desirable that the entire circulated electrolyte liquid flows through the electrode and that there no leakage or no electrolyte liquid can bypass the electrode. Apart from leakages, in particular the regions between the electrode and the rim of the frame or the rim of the opening are problematic because it was found that between electrode and frame, a flow channel can be formed and therefore electrolyte liquid flows past the electrode and through the cell without being used.
From JP 2006-324 129 A, a frame of a redox flow battery is known which has an opening in which an electrode is inserted. Electrolyte liquid is supplied to the cell or discharged via distribution channels ending in said opening. In order to prevent that electrolyte liquid flows between frame and electrode, it is provided here to arrange a projection on the frame, wherein said projection extends into the opening and extends into a recess of the electrode. The electrode rests against the projection. However, up to said projection, the electrolyte liquid can still freely flow past the electrode, whereby a portion of the electrolyte liquid still remains unused.
Therefore, it is an object of the present invention to provide a frame of a cell of a redox flow battery which improves the utilization of the electrolyte liquid circulated by the cell.